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| United States Patent |
5,020,312
|
|
Watakabe
|
June 4, 1991
|
Tire steel cords and method of manufacturing thereof
Abstract
A tire steel cord formed of more than three strands twisted together, at
least one of the strands being marked so as to formed therein with
zig-zagging marked parts which form gaps between strands, rubber
accordingly immersing the steel cord into its center part through the thus
formed gaps so as to fill in a cavity in the center part of the steel
cord.
| Inventors:
|
Watakabe; Hidenori (Yamaguchi, JP)
|
| Assignee:
|
Kokoku Steel Wire Ltd. (Tokyo, JP)
|
| Appl. No.:
|
428225 |
| Filed:
|
October 26, 1989 |
Foreign Application Priority Data
| Current U.S. Class: |
57/200; 57/311; 57/902 |
| Intern'l Class: |
D07B 001/06; D02G 003/48 |
| Field of Search: |
57/200,206,258,311,902
|
References Cited
U.S. Patent Documents
| 916048 | Mar., 1909 | Smith | 57/200.
|
| 1615790 | Jan., 1927 | Forbes et al. | 57/200.
|
| 4258543 | Mar., 1981 | Canevari et al. | 57/902.
|
| 4333306 | Jun., 1982 | Yamashita et al. | 57/206.
|
| 4385486 | May., 1983 | Iwata et al. | 57/311.
|
| 4715419 | Dec., 1987 | Kawasaki | 57/902.
|
| 4718470 | Jan., 1988 | Kusakabe et al. | 57/902.
|
| 4738096 | Apr., 1988 | Hatakeyama et al. | 57/206.
|
| 4790129 | Dec., 1988 | Hutchins | 57/206.
|
| 4938015 | Jul., 1990 | Kinoshita | 57/200.
|
| Foreign Patent Documents |
| 62-282293 | Dec., 1987 | JP.
| |
Primary Examiner: Hail, III; Joseph J.
Attorney, Agent or Firm: Klauber & Jackson
Claims
What we claimed is:
1. A steel tire cord comprising more than three strands of wire, each
strand extending in a longitudinal direction thereof, said strands of wire
being twisted together, and at least one of said strands extending in a
zig-zagging manner along the longitudinal direction thereof so as to form
sharp angles therealong, said tire cord having gaps in a center thereof
corresponding to positions of the angles.
Description
BACKGROUND OF THE INVENTION
The present invention relates to tire steel cords adapted to be embedded in
a belt section of a tire, and also relates to a method of manufacturing
thereof.
DESCRIPTION OF THE PRIOR ART
A conventional open-twisted steel cord is formed of strands which are
twisted together with gaps being formed between all or a part of the
strands. Then the steel cord is impregnated with rubber which enters
through the gaps and completely fills in a cavity in the center part of
the steel cord in order to prevent occurrence of the problem of rust that
is caused by moisture having entered into a cavity in the center part of a
steel cord and that has been inherent to non-open twisted steel cords.
That is, the occurrence of rust is eliminated by the rubber filled in the
cavity and preventing moisture from entering into the cavity.
However, it has been found that the following problem is inherent even to
the above-mentioned open-twisted steel cord, which cannot be imagined in
the nonopen-twisted steel cord:
In the open-steel cord, gaps which allow rubber to enter therethrough into
the center cavity of the cord are required between the strands, and
accordingly, large marking is required throughout the entire length of the
steel cord in order to form such gaps, causing non-uniform twist-in
lengths of the strands. As a result, the strands possibly shift
thereamong, and twisting is likely unstable in the longitudinal direction
of the cord, causing large concavities and convexities in a cut
cross-sectioned surface of the steel cord, and an excessive elongation
under a lower load, resulting in difficulty in working during embedding
cords in the belt section of a tire.
Further, upon manufacturing, strands are twisted loosely in order to form
structure parts, which inevitably causes unstable twisting. That is, there
has been such a problem in manufacture that the strands are unable to be
twisted in tight.
SUMMARY OF THE INVENTION
The present invention is devised in view of the above-mentioned problems,
and therefore, an object of the present invention is to provide a tire
steel cord and a method of manufacturing a tire steel cord which has
stable twist with satisfactory immersion of rubber and less elongation
under a low load.
To the end, according to the present invention, there is provided a steel
cord having more than three strands twisted together, characterized in
that at least one of the strands is formed with substantially zig-zagging
marked parts along the longitudinal direction.
It is preferable to form 0.05 mm or greater of gaps among the strands due
to the provision of the marked parts.
Further, it is preferable to have pitches of 2 mm or more of the marked
parts, which is not less than the value twice as large as the pitches of
twisting of the strands although the relationship between the pitches of
the marked parts and the pitches of twisting of the strands may be taken
arbitrarily. In the case in which the pitches are less than 2 mm; it is
difficult to maintain the gaps between the strands 0.05 mm or more, while
in the case in which the pitches exceed the value twice as large as the
pitches of twisting of the strands, spaces in parts through which rubber
enters exceed the pitches of twisting of the strands.
Further, in the case of two wires or more each having marked parts, the
marked parts among the strands may not only be aligned with each other in
the longitudinal direction so that they are adjacent to each other in the
circumferential direction, but also be shifted from each other in the
longitudinal direction so that they are not adjacent to each other.
Further, according to the present invention, there is provided a method of
producing the above-mentioned steel cord, characterized by the steps of:
passing one or more of strands which are three or more, between meshed
tooth surfaces of a pair of gear-like marking elements so as to mark the
strands in a zig-zagging shape, and thereafter, passing the strands into a
twisting machine so as to twist the strands. The pitches of teeth of the
marking elements and the configuration of the tooth surfaces thereof can
be suitably selected in accordance with desired pitches and shape of the
marked parts of the strands to be twisted. For example, in the case in
which two or more strands are marked, pitches and shapes of the marked
parts are suitably selected so as to be identical with each other or to be
different from each other.
Thus, gaps are formed between the marked parts and unmarked parts or
between the marked parts, which are adjacent to each other while the
strands make close contact with each other with no gap in the remaining
parts of the strands.
Accordingly, more than one gap between the marked part is formed in the
circumferential direction, and they are present at the pitches of the
marked parts in the longitudinal direction, thereby it is possible to
ensure entrance of rubber along the longitudinal direction.
Further, the strands can be twisted together in tight so as to make close
contact with each other so as to be held in a stable twisted condition.
The present invention will be detailed in an embodiment form with reference
to the accompanying drawings in which:
BRIEF DESCRIPTION OF THE DRAWINGS:
FIG. 1 is a front view illustrating a tire steel cord in one embodiment
form of the present invention;
FIG. 2 is a transverse sectional view along the line II--II in FIG. 1;
FIG. 3 is a front view illustrating a strand of the cord shown in FIG. 1;
and
FIG. 4 is a manufacturing machine used for carrying out a method of
manufacturing a tire steel cord according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1 in which a tire steel cord A is shown, the tire steel
cord A is formed by twisting five strands 1 each of which is marked so as
to have substantially zig-zagging marked parts 2 along the longitudinal
direction thereof. Gaps 4 communicated with the center part 3 of the cord
are formed at positions of the marked parts 2 in the strands 1. The
remaining parts of one strand 2 are made in close contact with those of
the other strands 2 with no gaps therebetween.
The following table shows the comparison between the tire steel cord
according to the present invention and conventional steel cords with data
of rubber immersion, stability in twisting and initial elongation.
__________________________________________________________________________
PRESENT INVENTION
CONVENTIONAL STEEL CORD
(1 .times. 5 .times. 0.23 mm),
NONOPEN CORD
OPEN CORD two strands having
(1 .times. 5 .times. 0.23 mm)
(1 .times. 5 .times. 0.23 mm)
marked parts
__________________________________________________________________________
RUBBER No Satisfactory
Satisfactory
IMMERSION
STABILITY IN
Satisfactory
No Satisfactory
TWISTING
INITIAL Small Large Small
ELONGATION
__________________________________________________________________________
The table shows that the steel cord according to the present invention is
stable and satisfactory in rubber immersion and twisting, and has a small
and slight initial elongation, and accordingly is excellent in total.
FIG. 4 exemplifies a manufacturing apparatus B developed for carrying out
the method of manufacturing steel cords according to the present
invention, in which strands 1 drawn for bobbins 5 are led to marking
elements 7 by way of a guide roller 6, and are then made to pierce through
through-holes in a stationary batten plate 8 after passing between meshed
tooth surfaces 7a of the marking elements 7, before being introduced into
a twisting machine 9 for twisting the strands into a steel cord.
The marking elements 7 are composed of a pair of gear-like members made of
metal, hard synthetic resin or the like, and rotated, being driven in
association with the travel of the strands 1 or by drive power from a
power source or the like.
Explanation will be made of manufacture of the tire steel cord A shown in
FIG. 1 with the use of the above-mentioned manufacturing apparatus B.
The strands 1 having been drawn from the bobbins 5 and guided by the guide
roller 6, are marked while they pass between the tooth surfaces 7a of the
marking elements 7 so as to form therein substantially zig-zagging marked
parts 2, and thereafter, are led to the twisting machine 9 after passing
through the through-hole in the batten plate 8, being twisted into a steel
cord A having gaps 4 at positions of the marked parts 2.
Further, in the case of such a configuration that strands 1 having marked
parts 2 and strands 1 having no marked parts are twisted together, the
strands 1 having no marked parts are led directly to the batten plate 8
from the guide roll 6, bypassing the marking elements 7.
Accordingly, the present invesntion has the following advantages:
(1) In a twisted structure in cross-section gaps communicated to the center
part of the steel cord are present at the positions of the marked parts of
the strands while remaining parts thereof other than the marked parts are
twisted in close contact with each other, thereby to give a tightly
twisted structure;
(2) Rubber surely and easily immerses the steel cord into the center part
thereof, eliminating the problem of rusting and stabilizing the twist of
the steel cord, and the elongation under a lower load is small, enhancing
the working ability in embedding steel cords in the belt section of a
tire;
(3) The steel cords according to the present invention can be
mass-produced; and
(4) The strands can be tightly twisted and therefore, steel cords having
gaps with desired dimensions can be uniformly manufactured.
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